The invention relates to exhaust manifolds and cooling systems for internal combustion engines and more particularly to those manifolds and systems adapted for use with marine engines.
Internal combustion engines have long been employed as powerful inboard motors for propelling boats especially in salt water environs. Both in-line and V-type marine engines are utilized extensively with automobile and truck engines being commonly adapted for marine purposes. However, adaptation of internal combustion engines, originally designed for land propulsion, to use in a marine environment poses several problems which necessitate significant modifications. One of the more important modifications in transforming an automobile or truck engine into a marine engine (or in building a dedicated marine engine) is made to ensure adequate engine cooling. In a typical water-cooled automotive engine, heat is removed from the engine by transfer to fresh water or coolant which is then in turn cooled by air blowing through the vanes of a radiator. However, this cooling system is inappropriate for marine engines which are often located in an enclosed area away from adequate air flow. U.S. Pat. Nos. 2,060,187 (Fernstrum) and 4,133,284 (Holcroft) describe a commonly employed method of marine engine cooling which transfers some of the water surrounding a boat through the cooling system with subsequent expulsion of the heated water back into the river, bay or surrounding body of water. This method known as the "raw water system" has proved to be extremely corrosive to marine engines being used in salt water. Also, sea water tends to precipitate salt out of solution at temperatures which are below the optimum for operating marine engines. Salt has been found to precipitate out at temperature in excess of about 140.degree.-150.degree. F. This salt precipitate obstructs cooling passageways by caking, contributes to destructive corrosion and forms an insulating scale which acts to reduce heat transfer efficiency. Recognition of the aforementioned problems has caused the development of marine cooling systems in the prior art which has known as "fresh water systems" in which raw water is passed through a heat exchanger rather than the engine block and then expelled. In the heat exchanger the raw water absorbs heat from a separate stream of recirculating coolant without commingling. Therefore, coolant or fresh water is recirculated through the engine block and cooled by heat transfer through a raw water fed heat exchanger. In the fresh water system, the fresh water circuit may be pressurized with thermostat control to optimize engine operating temperatures. In most prior raw water and fresh water systems, raw water is passed through a jacket surrounding the exhaust manifold before expulsion to the sea or surrounding body of water. The great hazard of boat fires place an increased emphasis on maintaining safe exhaust manifold temperatures. One type of fresh water system is described in U.S. Pat. No. 4,187,678 (Herenius).
These above commonly employed cooling systems for marine engines generally utilize many separate components which require extensive plumbing thereby making prior art systems expensive, cumbersome and complicated to maintain and repair. Corrosion continues to be a problem which necessitates costly and time consuming repair, cleaning or replacement of multiple component systems. Typical prior art systems use plumbing having one or more of the following disadvantages: (1) too many conduits (more expensive, cumbersome, labor intensive installation and/or replacement); (2) use of conduits having a small diameter (increased susceptability to obstruction); (3) conduits are too long (more expensive, increased surface area for conduit failure e.g. by corrosion or chemical degradation, obstruction of access to other engine components thereby increasing labor for maintenance and upkeep); and/or (4) galvanic corrosion by having dissimilar metals connected by an electrolytic solution (e.g. salt water).
An inexpensive, low maintenance, easy to install, long lasting system and apparatus which ameliorates many of the aforementioned problems has been discovered and forms the present invention as described below.